Abstract

We report an integrated photon pair source based on a CMOS-compatible microring resonator that generates multiple, simultaneous, and independent photon pairs at different wavelengths in a frequency comb compatible with fiber communication wavelength division multiplexing channels (200 GHz channel separation) and with a linewidth that is compatible with quantum memories (110 MHz). It operates in a self-locked pump configuration, avoiding the need for active stabilization, making it extremely robust even at very low power levels.

Figures (6)

(a) Experimental setup. The microring is embedded in an external cavity including a gain medium (EDFA), a band-pass filter (centered at the pump wavelength), and a polarization controller. Lasing is initiated by the ASE of the amplifier, which is fed back to the amplifier by means of 1x2 DWDM filter (H26 in the figure). The Fabry-Perot filter (FPF) selects only one of the external cavity lines. The signal/idler photon pairs exiting the drop port are transmitted through the high-isolation notch-filter, separated by a commercial DWDM filter, and then characterized by coincidence detection. (b) Spectrum of the above-threshold OPO showing the five different signal/idler (s5-s1 and i1-i5, respectively) couples detected in our experiment. The black curve represents the pump, while the grey traces are due to the noise of the optical spectrum analyzer.

(a) Measured coincidence peaks at five channel pairs centered around the pump wavelength. Clear coincidence peaks with a measured 110 MHz bandwidth (2.9 ns) are visible in all channel pairs. The solid-shaded curves are the g(2) fits of the experimental data (black curves). (b) Coincidence count rates measured at all the signal/idler combinations. Significant coincidence counts (corresponding to a peak) are only visible between symmetric channels (those with equal indices m,n for both signal, sm, and idler, in). For these measurements the idler detector was triggered by the signal detector (operating in free running mode).

(a) Idler-idler autocorrelation showing a bunching peak of 1.537 (corresponding to 1.86 effective modes). The black line represents the g(2) fit according to Eq. (1). (b) Heralded idler-idler autocorrelation. The antibunching dip of 0.144 ± 0.008 demonstrates the single photon character of the heralded source. The error bars are evaluated as the standard deviation on a 6-bin ensemble.

Cross correlation functions obtained when extracting the photons from two different ring ports. (a) Cross correlation function measured when selecting the photons at 1564.3 nm (H16, i5) at the through port and at 1548.1 nm (H36, s5) at the drop port (blue dots), with the corresponding gsi(2) fit (black curve). (b) Same as in (a), but with the frequency filters inverted.